| 摘要 |
PROBLEM TO BE SOLVED: To obtain excellent chemical convertibility even under the chemical conversion treatment conditions identical with those for a steel material by water-cooling an Al alloy material after hot working or after solution heat treatment and forming an oxide film having a specific thickness and containing a hydroxyl group showing a specific spectrum by absorbance indication on the surface of the Al alloy material. SOLUTION: An Al-Mg-Si type Al alloy material containing, by mass, 0.2-1.8% Si and 0.2-1.6% Mg is water cooled after hot working and/or solution heat treatment to obtain an Al alloy material to be coated after chemical conversion treatment. By this procedure, an oxide film of <=100Åthickness is formed on the surface of the Al alloy material. A hydroxyl group in this oxide film is controlled so that the spectral peak height occurring in the wave number part of 3500 K (cm-1), when the base line is from 3700 K to 2700 K, becomes <=0.007, at the time when FTIR analysis using a parallel polarized light of 75 deg angle of incidence is applied to the oxide film and the spectrum of the hydroxyl group is subjected to absorbance indication.
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